Corrosion Resistance and Weldability a Challenge for Duplex Filler Metals

Transcription

1 Corrosion Resistance and Weldability a Challenge for Duplex Filler Metals HIGH PERFORMANCE STEEL AND WELDING SOLUTIONS FOR HARSH ENVIRONMENTS VOESTALPINE OIL AND GAS EVENT HOUSTON, OCTOBER 2018 Bernd Hoberg Global Application Engineering Group Hamm, Germany 1 vabwg I SDSS Welding I

2 Corrosion Resistance and Weldability a Challenge for Duplex Filler Metals Content: Characteristics of DSS and SDSS Welding Procedures vs. Tendency to Pore Formation Corrosion Testing Conclusion 2 vabwg I SDSS Welding I

3 Material Selection e.g. for Seawater Environments Titanium: grade 2 grade 12 Nickel Alloys: Alloy 625 C-Alloys, e.g. 59, C-276 etc. Super Austenitic Stainless Steels SDSS 2507 type UNS Stainless Steels: Austenitic Stainless Steels DSS 2205 type UNS vabwg I SDSS Welding I L - X1NiCrMoCuN resistance against seawater at ambient temperature 904L - X2CrNiMoCu L - X2CrNiMo L - X2CrNiMo L - X2CrNi19-11 increasing corrosivity

4 25Cr - SDSS Interactive Requirements NORSOK MDS 52 (rev.4) PRE N Cr%+3,3Mo+16N% 40 Ferrite 35-65% WM Rp 0,2 >550, Rm >795MPa, A > 25% CVN -46 C > 45J CPT: ASTM G48 A: 50 C/24h no pits, < 4,0 g/m 2 => WM/BM ASTM G 48 A + E 2003 A: 6 mass-% FeCl 3 E: 6 mass-% FeCl 3 +1%HCl CPT: BM and WM Start temp 20 C / 24h T: 5 C / 24 h NACE MR PRE N Cr%+3,3(Mo+0,5W)+16N% 40 < PRE N 45; ferrite 35-65% H 2 S: 20 kpa Max. working temp 232 C Cast and wrought products NORSOK M-601(2016) Ferrite 30 to 70% WM CVN -46 C: 27 J WM + FL CPT ASTM G 48 A: 35 C/24h WM no pits, < 4,0g/m 2 WM Hardness max 36 HRC (DIN EN ISO ) 4 vabwg I SDSS Welding I ASTM A corr. test temp.* BM: 40 C/24 h CVN -40 C BM, WM: negotiable! *) detection of intermetallics e.g. sigma phase

5 22Cr - DSS Interactive Requirements ASTM G 48 A 2003 NORSOK MDS 42 (rev.5) UNS S31803, UNS S Ferrite 35-65% WM Rp0,2 > 450, Rm > 620MPa, A > 25% CVN -46 C > 45J CPT G 48 A: 25 C/24h WM < 4g/m2 WM 5 vabwg I SDSS Welding I NORSOK M-601 (2016) Ferrite 30 to 70% WM CVN -46 C: 27 J WM+FL Hardness max 36 HRC (DIN EN ISO ) Method A: 6 mass-% FeCl 3 CPT: 25 C/24 h WM + BM NACE MR PRE N Cr%+3,3(Mo+0,5W)+16N% 30 PRE N 40: ferrite 35-65% H 2 S: 10kPA Max. working temp 232 C Cast and wrought products ASTM A corr. test temp.* BM + WM:22 C/24 h CVN -40 C BM, HAZ: 54J, WM 34 J *) detection of intermetallic s e.g. sigma phase

6 Corrosion Resistance and Weldability a Challenge for Duplex Filler Metals Content: Characteristics of DSS and SDSS Welding Procedures vs. Tendency to Pore Formation Corrosion Testing Conclusion 6 vabwg I SDSS Welding I

7 GMA Welding / (MIG/MAG) Process: from manually assisted to fully automatic Shielding gases: inert/active; Ar, He and/or CO 2 and their mixtures Advantages: high deposition rates and welding speed, low heat input possible Disadvantages: positioning of the torch, spatter and weld defects e.g. lack of fusion and porosity SDSS PRE N > 41) Welding Consumables: Thermanit 22/09, Thermanit 25/09 CuT CN 22/9-IG CN 25/9 CuT-IG 7 vabwg I SDSS Welding I

8 Influence of the Shielding Gas on Droplet Transfer and Arc Mode Spray arc Fine droplets without short circuit Shielding gas: Ar and mixed gases e.g. Ar/He/CO 2 - bal/30/0,5 Welding position: PA (1G), PB (2G) Typical parameters (1.2 mm ø): I = 270 A, U = 29 V, V wire 8 m/min Pulsed arc Droplet segregation through "pinch effect" Pulse time, voltage, current and pulse background must be adjusted Shielding gas: Ar and mixed gases s.o. Base metals: CRA, nickel alloys, aluminum reduction Welding position: PA (1G), PB (2G), PF (3Gu) wire of area electrode 8 vabwg I SDSS Welding I magnetic field

9 SDSS vs. 300 Series Stainless Steel - GMAW Fluidity and arc stability are not as good as than standard austenitic fillers (spatter) Best results with synergic pulse GMAW Recommended shielding gas for SDSS: Ar % He + 0,5 % CO 2 High BM nitrogen content influences sensitivity to porosity: wrong joint preparation increases risk high degree of fusion & trapping of nitrogen gas in solidifying metal weld in a gap, root opening Pulsed arc Normal spray arc Spatter in short arc Spatter in short arc 9 vabwg I SDSS Welding I

10 Pore Formation in GMAW of SDSS Weld Metal Bead-on-plate welding: 2 layers, 4 runs Chg Chg vabwg I SDSS Welding I

11 Occurrence of Porosity during GMAW of SDSS Bead-on-plate welding: 2 layers, 4 runs Chg vabwg I SDSS Welding I

12 SA Welding - Wire Flux Combination DSS: Thermanit 22/09 + Marathon 431 CN 22/9 IG + Flux 805* SDSS: Thermanit 25/09 CuT + Marathon 431 CN 25/9 CuT-IG + Flux 805* 12 vabwg I SDSS Welding I *)PWHT solution annealing

13 SA Welding with SDSS Wire Electrode Thermanit 25/09 CuT Features: one wire electrode one power source one control ~ 25 mm Advantages: high deposition rate Typical welding parameters: wire electrode diameter: 2,0 mm (preferred) - 2,4mm (max) current / voltage A / V welding speed: cm/min interpass temp: 100 C heat Input: max. 12 kj/cm flux: Marathon 431 (basicity 2,3 ). 13 vabwg I SDSS Welding I

14 Pore Formation in SA Welded SDSS All Weld Metal Sample All weld metal test specimen acc. EN ISO Heat no.: Heat no.: vabwg I SDSS Welding I

15 Typical Properties SA Welded Sample a) Chemical composition of base material and weld metal Base Materials C Si Mn P S Cr Mo Ni Al Cu N Ti Nb UNS / x2000x15 L Thernanit 25/09CuT Thernanit 25/09CuT JK Marathon x400x / solution annealed 1120 C / 22 min / water wire electrode XDM all weld metal b) Mechanical properties of base material and weld metal Test Specimen Dimension Heat-no. Sample no. Tensile Test ReH / Rp1,0 Rm A5 CVN - 20 Charpy Impact Test [J] CVN -CVN -CVN -CVN -CVN -CVN -CVN -CVN SBB 4,0 Bend Test d/a RBB 4,0 FBB 4,0 Remark UNS / x2000 x15 L solution annealed 1120 C / 22 min / water Thermanit 25/09 CuT 2,0 mm Marathon x400 x / K BM OK 180 OK 180 OK all weld metal c) Optical microscopy BM FL WM 15 vabwg I SDSS Welding I

16 Corrosion Resistance and Weldability a Challenge for Duplex Filler Metals Content: Characteristics of DSS and SDSS Welding Procedures vs. Tendency to Pore Formation Corrosion Testing Conclusion 16 vabwg I SDSS Welding I

17 Critical Crevice Temperature (CCT) - Critical Pitting Temperature (CPT) DSS 904L SDSS Alloy 31 Alloy 24 AL-6XN Pitting Corrosion 316L Crevice Corrosion ASTM G 48 A. CRA test specimens will be examined in 6% FeCl 3 testing solution at constant temperature and testing time, for example 24 h. 17 vabwg I SDSS Welding I

18 Precipitation Behavior of (S)DSS 1000 Temperature [ C] 300 Cr Mo W Si Mo, W, Si Cr, Mo Cu,W M 7 C 3 - Carbide CrN - Nitrid s - Phase Cr 2 N - Nitride c - Phase g 2 - Phase M 23 C 6 - Carbide p - Phase e - Phase a - Phase G - Phase Cr, Mo, Cu, W Time [h] Properties of GTA weld metal: DSS: Thermanit 22/09 SDSS: Thermanit 25/09 CuT DSS SDSS Cr 22,7 25,3 Mo 3,3 3,7 N 0,16 0,24 PRE >35 >41 YS (MPa) TS [MPA] Elong. [%] CVN [J],-40 C >100 > vabwg I SDSS Welding I

19 Corrosion Testing acc. to ASTM G 48 E Sample Preparation Machined test specimen Final layer: as welded, brushed Cut edges ground with grid 80 wet ASTM G 48, Method C and E 6% FeCl 3 + 1% HCl Test 24 h (attn. method C 72 h!) Start temp 20 C T: 5 C/24 h Detection: Critical Pitting Corrosion (CPT) Calculation: Corrosion rates e.g. mm/year or g/m 2 19 vabwg I SDSS Welding I

20 ASTM G 48 E - Results of various Thermanit 25/09 CuT Weld Deposits 20 vabwg I SDSS Welding I

21 Corrosion Resistance and Weldability a Challenge for Duplex Filler Metals Content: Characteristics of DSS and SDSS Welding Procedures vs. Tendency to Pore Formation Corrosion Testing Conclusion 21 vabwg I SDSS Welding I

22 Cold - Pass - Technique for SDSS HEAT INPUT = Cold-Pass Bulky Root I x U x 60 [KJ/cm] V S x 1000 HI: 8-12 kj/cm HI: kj/cm 22 vabwg I SDSS Welding I High thermal loading on the root pass increases the risk for: precipitation of intermetallic phases! reduced corrosion resistance

23 Influence of Heat Input Slow cooling rate in the case of H I > 15 kj/cm HEAT INPUT = I x U x 60 V S x 1000 [KJ/cm] Increased risk of precipitation of intermetallics (sigma, chi) Structural instability Decreased corrosion resistance Decreased toughness Avoid high heat input in hot pass to minimize sigma in root bead Cold Pass Interpass temp. < 120 C for DSS < 100 C for SDSS Bulky Root 23 vabwg I SDSS Welding I

24 Welding of Super Duplex Steel Procedures and consumables: GTAW: wire rod PRE N 41 (Norsok Calc.) for CPT requirements C! SAW: see above but don t accept CPT > 35 C for joint welding (heat input!!!) GMAW: wire electrode PRE N to reduce porosity problems; FCAW is an alternative => Avesta FCW 2507/P100-PW NOR! SMAW: PRE N > 40 (Norsok Calc.) to achieve proper corrosion resistance Welding practice and workmanship: Root and 1. and 2. layer: GTAW Shielding gas: Ar + 2 %N 2 (FM with PRE N > 42 pure Ar to avoid porosity) Purging gas: Ar + 2 %N 2 or 95 N H 2 Interpass temperature: max. 100 C right handling ensures a safe environment Heat input: root: layer all others: 8-15 kj/cm 5-12 kj/cm 5-12 kj/cm Tack welding: welding on the root side not permitted 24 vabwg I SDSS Welding I

25 Thank you! Bernd Hoberg T. +49/ vabwg I SDSS Welding I